 However, the Illinois Department of Transportation (IDOT) has always and continues to report the Skyway as part of the Interstate Highway System, and the Federal Highway Administration also considers the Chicago Skyway an official part of I-90.In the 1960s, the newly constructed Dan Ryan Expressway and the neighboring Calumet Expressway, Kingery Expressway and Borman Expressway provided free alternatives to the tollway, and the Skyway became much less used.As a result, from the 1970s through the early 1990s, the Skyway was unable to repay revenue bonds used in its construction.